apache2 无法重新启动

系统：ubuntu server 14.04 LTS
服务：apache2
重启服务时报
 * Restarting web server apache2                                                                                             AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message

解决方案：
cd /etc/apache2/sites-enabled
sudo vi 000-default.conf

打开default文件后，在default文件顶端加入：

ServerName 127.0.0.1

重启apache2 (sudo /etc/init.d/apache2 restart)就不会提示上述错误了。